The present invention relates to double side grinding apparatus for thin disklike work, and more particularly to an apparatus for simultaneously grinding opposite surfaces of thin disklike work such as semiconductor wafers.
Apparatus for grinding opposite surfaces of work at the same time are already known which comprise a pair of rotatable grinding wheels having respective grinding end faces opposed to each other for positioning the work as placed in a pocket (aperture) of a rotatable disklike carrier. In this case, the grinding faces of the wheels need to be greater than the work in outside diameter. The carrier is usually formed with a plurality of pockets as equidistantly spaced apart and arranged on a circumference closer to the outer periphery of the carrier. While a portion of the carrier is positioned also between the pair of grinding wheels along with the work, the thickness of this portion of the carrier must of course be smaller than the distance between the pair of wheels as positioned for grinding, i.e., the thickness of the finished work.
The semiconductor wafers present in use include those measuring about 200 mm (8 inches) and those measuring about 300 mm (12 inches) in outside diameter. The wafers of either type (as finished by grinding) have a thickness of about 0.8 mm which is extremely small as compared with the outside diameter. For use in grinding such wafers which are relatively great in outside diameter, the grinding wheels have an increased outside diameter, and the carrier to be rotated with the wafer accommodated therein also has an increased size, consequently rendering the apparatus large-sized. Further because the wafers are thin, the carrier portion to be positioned between the grinding wheels along with the wafer must be greatly reduced in thickness. The grinding force acts on the carrier placed between the grinding wheels, especially on the pocket portion thereof, through the work accommodated. When reduced in thickness, this portion has impaired strength and encounters difficulty in smoothly moving the work. For this reason, it has been difficult to grind opposite surfaces of wafers.
The same problems as above are also experienced with thin disklike workpieces other than wafers.